Aircraft control apparatus



May 31, 1949. R. J. KUTZLER ET Al.

AIRCRAFT CONTROL APPARATUS 2 Sheets-Sheet 1 Filed Dec. so, 1944 May 31,1949.

Filed Dec. 30, 1,944

R. J. KUTZLER ET AL AIRCRAFT CONTROL APPARATUS 2 `Sheets-Sheet 2 BY@6fm/WISY Patented May 31, 1949 UNITED STATES PATENT OFFICE AIRCRAFTCONTROL APPARATUS Robert J. Kutzler and Theodore J. Wilson, Minneapolis,Minn., assignors to Minneapolis- Honeywell Regulator Company,Minneapolis, Minn., a corporation of Delaware Application 'December 30,1944, Serial No. 570,712

The present invention is concerned with aircraft control apparatusandmorel particularly with apparatus for manually modifying the action ofan automatic night control system whenever departure of the aircraftfrom a predetermined course is desired. Y i

In automatic systems for controlling the night of an airplane, it isnecessary to provide some means under the control of the pilot`for'modifying the direction of Iiight in either a horizontal orvertical direction or both to permit turning or climbing as desired. Itis broadly an object of thepresent invention to provide such a manuallyoperated means which is convenient 'to operate and provides a means forreadily maneuvering the aircraft with the aidof the automatic controlsystem.

A further object of the invention is to provide such an arrangement inwhich a tiltable member is provided which upon being tilted in onedire'ction affects the turning of the aircraft and which upon beingtilted in a different direction affects the pitch of the aircraft.

A still further object of the present invention is to provide such anarrangement in which upon the manually movable member being moved in onedirection both the airfoil surface controlling the direction of flightand that controlling'the tilt of the aircraft about itsV longitudinalaxis are operated to place the airplane in a banked turn.

A further object of 'the invention isto provide a manual control meansfor an automatic i'ght control system inwhich upon the manual con-y trolmeans being released, it automatically returns to the position assumedbefore the desired operation.

A still further object of the present invention is to provide such amanual control means which when moved in one direction causes the-planeto be placed in a banked turn and when moved in another direction to`place the plane in aturn without banking.

A still further object of the presentfinvention is to provide inconnection with a-manually controlled arrangement for modifying theaction of an automatic flight control system, means for rendering thedirection responsivefdevice-temporarily inoperative during a turnand'for maintaining the same inoperative for a peridfoftime after themanual control means is restored to its normal position.

A still further' object of the present rvinvention is to provide animproved device for selectively operating a plurality of impedanceunits, de-

21 Claims.

2 peiccling upon the direction in which a handle is til e A furtherobject of the present invention is to provide a means for manuallyoperating a plurality of potentiometers depending upon the direction oftilt of a handle member.

Other objects of the present invention will be apparent from aconsideration of the accompanying speciication, claims'and drawing, ofwhich Figure l is a schematic view of a night control system employingour improved manual control,

Figure 2 is a vertical sectional view of our i'mproved manual control,

m Figure 3 is a View taken along the line 3 3 of Figure 2 in thedirection of the arrows adjacent that line,

Figure 4 is a View taken along the line 4--4 of Figure 2 in thedirection of the'arrows adjacent that line, and

Figure 5 is a detailed view partly in section of a portion of the switchactuating mechanism of our manual control.

Referring to the drawing, we have shown in Figure l, as above noted, aflight control system employing our manual control. In this" system,there are three motors ID, I I, and I2 for operating'` the ailerons, therudder, and the elevator, respectively. These three motors may be of anyconventional type capable of being reversibly controlled by the outputof an amplifier. Each of these three motors is connected to amplifiersI3, I4, or I5, respectively. The amplifiers are of any suitable typewhich are capable of supplying to an output circuit a voltage, the phaserelationship of which to a standard source of Voltage is dependent uponand reversible with thev signal voltage supplied to the amplifier.

Each of the amplifiers I3, I4, and I5 has supplied to it a signalvoltage which is derived from an impedance network. The impedancenetwork associated with the amplifier I3 is generally designated by thereference numeral I6, that'asreference numeral I8. These networks willnow be described.

Referring rst to the network l'controlling the amplifier Iwhich in turncontrols the aileron motor lil, the main portion of this networkconsists of two bridges I9 and 20. The bridge `2|) consists of agyroscopically operated potentiometer 2l and a followup potentiometer22. The gyroscopically operated potentiometer 2l consists of a' resistor24 and a slider 25. kThe slider 25 is r connected through a mechanicalconnection'26 (only schematically shown) to a vertical gyroscope 21. Thevertical gyroscope is effective whenever the aircraft in which it ismounted rolls with respect to its longitudinal axis to move slider 25 inone direction or the other with respect to resistor 24, depending uponthe direction of roll. The follow up potentiometer 22 likewise consistsof a resistor 28 and a slider 29. The slider 29 is operatively connectedto the motor i@ to assume a position dependent upon that of the motor.

The bridge including potentiometers 2| and 22 is energized by atransformer 3| and includes centering potentiometers 33 and 34 and aratio adjusting rheostat 32. The transformer 3| comprises a primarywinding 4!) and at least one secondary winding 4|. The control system ofour invention requires the use of a large number of eiectricallyisolated sources of alternating voltage. it is preferable to providecertain of these voltages from separate secondary windings of a singletransformer. For convenience in illustration, however, each secondarywinding is shown as associated with its individual primary winding. inorder to indicate that the windings may all be secondaries of the sametransformer, the primary winding of each transformer to be referred tohereinafter will be given the same reference character.

The centering potentiometers 33 and 34 consist of resistors 35 and 36with which cooperate sliders i? and 38, respectively. The sliders 3l andare connected together and to any suitable manual operator in such amanner that if the operator is turned, the sliders are moved in oppositedirections with respect to their associated resistors. Each of thesliders is connected to the upper terminal of its associated resistor soas to shunt the upper portion of the resistor above the point ofcontact. Due to the sliders moving in opposite directions, the amount ofresistance cut out of one potentiometer will be exactly equal to thatconnected into another potentiometer.

The resistors 24 and 28 of the gyroscopically operated and follow uppotentiometers 2| and 22 are connected in parallel to secondary 4|, theconnections of resistor 28 to secondary 4| including the resistors 35and 36 of the centering potentiometer. These last connections are asfollows: from the upper terminal of secondary 4| through conductor 42,resistor 3B, conductors 43 and 44, resistor 23, conductors 45 and 46,resistor 35, and conductor 4] to the other terminal of secondary fil.Thus, the resistors 35 and 3S of the centering potentiometers andresistor 28 form a series circuit, the effective midpoint of which isdependent upon the position of sliders 31 and 38 of the centeringpotentiometers. lThus, upon slider t? being moved upwardly and slider 38down wardly, the electrical midpoint of the series circuit just referredto is shifted from the center of resistor 28 to a point somewhat to theleft of center. Upon sliders 3l and 38 being moved in the oppositedirection, the electrical midpoint is shifted to the right.

The ratio adjusting rheostat 32 consists of a resistor 5i? and a slider5|. This rheostat is connected in parallel with resistor 2&5 of followup potentiometer 22 by conductors 44 and 45. By varying the position ofthe slider of rheostat the effect of potentiometer 22 relative to thegyroscopic potentiometer 2| is varied.

The bridge i9 consists of two gyroscopically operated potentometers di)and el, both of which are actuated by a directional gyroscope 62'. Thepotentiometer ti! comprises a center tapped resistor t3 and a slider t4.The gyroscopically operated potentiometer l comprises a center tappedresistor 65 and a slider tt. The two sliders iid and '$6 are connectedtogether and to the gyroscope 62 by mechanical connections schematicallyindicated by the reference numeral Controlling the movement of thisconnection is an electrically operated lock (iii which when. energizedprevents movement of the connection Eii. interposed between the lock E59and the gyroscope is any suitable slip friction connection or frictionclutch 'i2 which permits the gyroscope to turn with respect to the craftwhen the lock 69 is engaged. A transformer i0 comprising a primarywinding 4i! and a secondary 1| is employed to supply power to bridge i9.The upper terminal of this secondary is connected through conductors i3,i4, and 75 to both terminals of resistor The lower terminal of secondary1I is connected through a resistor '58, conductors 19 and 8B, and aresistor 8| to the center tap of resistor E3. The voltage acrosssecondary '|I is thus impressed between the opposite terminals ofresistor @It and the center tap thereof. The phase of the voltageappearing between the center tap and the slider G4 of potentiometer 60is not aifected by the direction of movement of sliders 64, since bothends of resistor E3 are connected together. The voltage appearingbetween the two points just mentioned is impressed across the resistort5, the center tap being connected by resistor Si and conductor 8E), toone terminal of resistor t5 while the slider |54 is connected byconductor 82 to the other terminal of resistor 65.

A trimmer potentiometer 84 comprises a resistor $5 and a slider 86. Theresistor 85 is connected between slider (it of potentiometer 6l and thecenter tap of resistor 65 by conductors 8B and 8g.

It will be noted from the above that the voltage appearing between thecenter tap and slider 64 of potentiometer 5t is impressed across theresistor (iii of potentiometer 6| and that the voltage between theslider and center tap of the latter potentiometer is in turn impressedacross resistor 85. This latter voltage will vary in accordance with themovement of both slider 64 and slider 66. Since these two sliders movetogether, it will be obvious that the voltage between slider 66 and thecenter tap of resistor 65 will tend to vary as 'the square of themovement of sliders 64 and 66 from their normal center position. Due tothe resister 3|, this variation is not quite as great as the square ofthe movement but does vary as an exponential function greater than one.The voltage between the lower terminal of resistor 85 and the slider 3%is thus a portion of this eX- ponential voltage, the magnitude of theportion being determined by the position of slider 86.

Before completing the description of the network associated with theaileron control circuit, network |71' will now be described, sincecertain elements are 4connected to both networks i6 and Va'.

The network comprises bridges 95 and |20. The bridge t5 comprises apotentiometer 96 having a center tapped resistor 9i and a slider 98. Avoltage is impressed across the terminals of resistor Si' by atransformer S9 having a primary winding 4d and a secondary winding Q9.The secondary winding is connected to the opposite terminals of resistor9i'. There thus appears be- 'f5 .tween :the slider and the center -tapof vthe resistorl9| avoltage the magnitude of which is dependentupon thedisplacementof slider S3 from the .center tap .and the phase of which isdependent upon the directionof suchdisplacement. A- 'trimming.potentiometer comprises a. resistor |62 and a slider |63. The upperterminal 'ofresistor |02 is connected by conductor |64 to slider l98 andthe lower terminal of resistor m2 is connected to the center tap ofresistor 91 by 'conductors |05 and |66. .There is thus impressed acrossresistor |62 a voltage which is dependent Xin magnitude and phase uponthe extent and di- 'rection of .displacement of slider 98 from the cen-'ter tap of resistor 91. A variable portion of this voltage appearsbetween the lower terminal of refsistor. |02 and the slider |03, themagnitude of fthisportiondepending upon the position of slider ':|||3.The bridge |20 is almost identical to the -bridge 20 of the network i6.For that reason, the Ynetwork and the various elements thereof haverbeenrgiven reference characters |66 higher than the correspondingelements of bridge 2d. Thus 'there is a gyroscopically operatedpotentiometer |2,| having a-resistor |24 and a slider |25. Simi- 1arly,there is a follow up potentiometer |22 hav- 'ingaresistor `|28 andaslider |29. The power is applied to the bridge by a transformer |3|having .a primary winding 40 and a secondary winding |`4,|. Thecenteringpotentiometers |33 and i3d p perform the same function with reference tothe bridge circuit as centering potentiometers 33 and '534. Similarly,`the ratio adjusting rheostat |32 adjusts the relativeeect of therebalancing potentiometer |22 and the gyroscopically operated lpotentiometer |2|.

The slider |25 of the gyroscopically operated potentiometer |2| ispositioned bythe directional -gyroscope under the control of the lock 69so that when this lock is released, any deviation of the l aircraftvfrom a predetermined direction of flight Awill causevmovementof slider|25 in one direction Aor the other. The resultant movement of the,slider |29 of follow up potentiometer |22 will be .in such a directionas to rebalance the bridge.

Associated with each f the two networks le rand I1 are a .plurality `of.other bridges. Disregardingthe bridges in our new manual controller,:there is a bridge l!) and a voltage dividing net- Work.|.5|. The.voltage dividing network I5! com- ,prises .two potentiometers |52 and|53. The potentiometer |52 includes a resistor I5@ and a slider .|55while potentiometer |53 includes a resistor .|56 anda slider |51. Theupper terminals ,ofresistors |54 and |56 are connected together byconductors |58 and |59, and the junction of these .conductors isconnected through a resistor |65) to Aground at |61. The lower terminalsof resistors |54 ,and |56 are connected together by conductors |63.and.|64. Slider |55 is connected to the aileron network and slider |51to the rudder network. "The 'junction of conductors |63 and liii is con-.nected to the bridge |50. This rbridge consists of amanually adjustablepotentiometer |66 having .a center tapped resistor |61 and a slider |66.A transformer |16 having a primary winding lil and 'a secondary winding|1| is employed to impress a voltage across resistor |61. The secondary"|.1| is connected across the opposite terminals of .resistor |61. Aslider |68 is positioned through 4mechanical connecting means |12 byaknob |13.

lThesame mechanical connecting means i12 also :extends to a cam |115which is adapted to position a switchblade |16 adaptedto be moved intocon- 4tactmaking engagement with a second switch 'slider 22d.

blade .I1-1. Upon .the .manual knob |13 being turned in Veither'directionaway from the central position to move slider `|63 in eitherdirection away from its contact with the center tap, the cam |15iseffective to move switch blade |16 upwardly into contact makingengagement with vswitch blade |11. Thus, the switch consisting of switchblades |16 .and |11 is closed upon knob |13 being actuated in eitherdirection. The po tentiometer |66 is employed as a turn control and isoperated when it is desired to make turns without the use of ourimproved manual controller. As will be explained in more detail later,the operation of this turn control causes the plane to be placed in aproperly banked turn with accompanying movement of both the rudder andthe ailerons. The potentiometers |52 and |53 are employed to adjust therelative amounts of rudder and aileron movement which take place andhence enable adjustment in order to insure that the turn is properlybanked.

The elevator contro1 network |6 will now be considered. This networkcomprises two bridges |90 and 226. Bridge |96 includes a potentiometer|9| and a transformer |62. The potentiometer |9| consists of a centertapped resistor |93 and a slider |94. The transformer |92 comprises aprimary winding 4i) and a secondary winding |166. The two terminals ofcenter tapped resistor |93 are connected together and to the upper-terminal of secondary |66 by conductors |61, |93, and |99 and resistor256. The center tap of resistor |93 is connected by conductors 26|! and203 to the lower terminal of secondary |96. The voltage of secondary |66is thus impressed between the center tap and either terminal of resistor|93. Movement of slider |925 in either direction away from the centertap causes a voltage to appear between the center tap and the sliderwhich is not aiected in phase by the direction of displacement of theslider from the center tap.

A potentiometer Eil@ consists of a resistor iti and a slider fil. Theopposite terminals of the potentiometer are connected to the slider iii@and to the center tap ci resistor |93 by conductors 265i, 260, and 262.There is thus impressed across the resistor till a voltage whichdependent in magnitude but not in phase upon the displacement of sliderfrom the center The slider |534 is operatively connected through themechanical connections 26 to the vertical gyroscope 21 and is operatedwhenever the ship rolls about its longitudinal axis. The voltage acrossresistor 261 is thus dependent upon the l nitride but not the directionof roll.

ine bridge 226 is very similar to the bridge |26 and hence has beengiven a reference numeral iii@ higher than that employed in connectionwith bridge The various elements of the bridge likewise have been givenreference characters |5353 higher than the corresponding elements ofbridge |26. Thus, there is a gyrcscopically operated potentiometer ilhaving a slider 225 and a resistor 22e. There is a follow uppotentiometer 222 having a resistor 228 and a The bridge is energized bya transformer V23| having a primary winding i9 and a secondary winding2LH. Centering potentiometers 233 and 236 and the ratio rheostat performthe same relative functions in the bridge as in bridges Z6 and |2|i.

In the case of gyroscopically operated potentiometer 22|, the slider 225is operated by the vertical .gyroscope through a mechanical connection249. This connection is-eiective to cause the slider to be movedwhenever the plane tilts about a transverse axis; that is, whenever theplane changes its pitch.

lFollow up potentiometer slider 223 is connected to the elevator motorl2 and is operated whenever` the motor i2 is energized as a result ofimbalance of the network. The eiect of the movement of slider 229 is totend to rebalance the network.

Our manual controller will now be described. controller is shown indetail in Figures 2 to 5, being shown schematically at the bottom ofFigure l. controller will rst be described as i'ar as the schematicshowing of Figure 1 is concerned. Located within a housing 25|] are aplurality of potentiometers 252, 253, and 254. These threepotentiometers are designed to be operated by a manually tiltable member255. The potentiometer is actuated when the member 2F is tilted in onedirection, the potentiometer when number 255i is tilted in a seconddirection, and potentiometer 253 when the member 255 is rotated aboutits longitudinal axis.

Also included within the housing 255 are a plurality oi potentiometers'251, 258, and 259. These potentiometers are employed as trimmingpotentiometers to adjust the effect of potentioz eters 252, 253, and252i, respectively. The .otentiometers 252 and 25? form part of a bridge255i, the potentiometers 253 and 258 part of a bridge and thepotentiometer-s 254 and 255 t ot bridge 2i52. The potentiometers inthese various bridges will now be described in detail,

Referring to bridge 2.@5, the potentiometer 252 consists of a centertapped resistor 255 and a slider The potentiometer 257| consists of aresistor and a slider 255. A transformer yupplies power to the bridge,this transformer ting of a primary winding @l and a secondary winding222. The opposite terminals of secondary winding 222 are connected tothe opposite terminals of resistor The center tap of resistor 265 isconnected by conductors 213 and 2Wl to one terminal of resistor 25'!while the slider 2555 is connected by a conductor 215 to the otherterminal of resistor 26'?. There is thus impressed across resistor 252 avoltage corresponding in phase and magnitude to the displaceeut ofslider from the midpoint of resistor xline right hand terminal ofresistor 251 is connected by conductor 2M to ground at Zl'. There isthus impressed between the slider 258 and und a voltage which isdependent in magnit :le upon the position oi slider 253 and dependent inmagnitude and phase upon the amount and direction of displacement ofslider from the mid-position of resistor 255. Referring now to thedetails of bridge the potentiometer 253 comprises a center tappedresistor 295 over which moves a slider 25H. Potentiometer 258 consistsof a slider 293 movable over a resistor 294. A transformer 2.95 is emyedto energize the bridge 2M. This transformer comprises a primary winding40 and a secondary winding 2%, the opposite terminals of secondarywinding 258 being connected to the opposite terminals of resistor 295.The slider 29| of potentiometer 253 is connected to the left handterminal of resistor 256i by conductor` 35|). The center tap of resistor2t@ is connected to the right terminal of resistor 255i by conductor30|. voltage which appears between slider 29| and the center tap of theresistor 290 upon displacement of slider 29| in either direction is thusiai prises a center tapped resistor 325 over which moves a slider Thepotentiometer 259 comprises a resistor till over which moves a slider328. The left hand terminal of resistor 301 is connected to the slider355 by conductor 309 and the right hand terminal is connected to thecenter tap or resistor te?) by conductor 3M). The bridge is energized bya transformer 3&2 having a primary winding cli and a secondary windingdit. The second nv winding is connected across the opposite terminals ofresistor 355 so that upon any movement of slider ttt in either d ction,voltage appears between the slider e the center tap. rE'nus the voltageaprire between the center tap and the slider is tol1 The right hand.istor s connected. by conductor at 3l l. There thus appears between lground a voltage which correspon .n in gnitude to the position of sliderin magnitude and phase to the extent and direction of the displacementof slider 306 with respect to its mid-position.

Our manual controlling apparatus also comprises a switch consisting oiswitch blades 3|5 and dit. Switch blade is associated with the manuallypositionable member 255 in such a manner that when this member isdepressed, switch blade is moved into engagement with switch blade 2lb.This switch is connected in parallel with the switch consisting ofswitch blades llt? and lill and controls the energization 'i of the lock59 for the gyroscope previously described.

Before proceeding further with a description of the operation of thesystem as a whole, the mechanical details of our manual controller willnow be described. Referring to Figure 2, the rectangular case 25@ isshown as a case having a removable bottom 225 and an aperture 325centrally disposed in the upper portion thereof. Extending through thisaperture is the rod 255 previously referred to. Surrounding this rod isa sleeve 322' which is si. rounded by a disl: 323 spring pressed intoengagement with the under side of the housing by a spring 329. The diskserves to provide a and yet permit sidewise movement of the member 255and the sleeve 32'?. A knob shown partly in section, is secured to theupper terminal of the member 255. A spring 53! is interposed between theupper end of sleeve l2? knob 53@ and urges the latter upwardly. The'upper portion oi the sleeve 321 is cylindrical in cross section whilethe lower portion beginning at point 232 is square in cross section.This square portion of the sleeve 321 is pivotally mounted upon arockable member indicated in its entirety by the reference numeral 331i.r1She rockable member 35d comprises two bar members and i332 which aresupported in spaced relation by interposed blocks 339 at each endthereof. Only one such block is shown,

1 9 .athis-being.illustratedin` Figure 4. The blocks 339 .farejournaledat their'opposite ends to abracket fimemberv 346 secured atseveral` spaced points to 'fthe housing 256. The rectangular portion of"sleevel321 extends between the-bars 336 and 331 .asl'best'shown inFigure 4. Disposed on the outl/side of bar 331 are a plurality ofwashers 34|., and "disposed on the outer sideof member 336 is a "I block343 which has aportion i344 of square cross -section. The assemblageconsisting-oi block 343, 'sleeve 321, and washers 34| is fastenedtogether 1=by a plurality of screws 346 and 341. 'These screws extendinto the sleeve 321 but do not enter the tiltable member 256 since it isessential that the latter member both reciprocate and rotate withrespect to the sleeve member 321. The *screws 3346 and 341,furthermore,v extend freely 'f through bar members 336 and' 331 topermit rock- "ing'of members 256,` 321. .and 343 with respect to '-'barmembers 336and It will be seen from 4vthe above that members'256 and 321are pivotally -secured to the rockable member 334 so that upon #knob 336being moved in the plane of the drawing-member' 256 and sleeve 321 arerocked without affecting the position of rockable member'334. If-,'onthe other hand, the knob 336 is moved in a direction at right angles tothe plane of the draw- "ing; the rockable member 334- is rocked.

The potentiometers 252 and 254 are designed to beselectively actuated bymovement of knob ""336 depending upon the direction in which it is"moi/ed.' Referring rst to the potentiometer 252, `the slider 266 issecured to the lower portion of sleeve'321. The resistor'265`is mountedat its `opposite`ends to the rockable member 334. Re-

ferring to Figure 4, it will be noted that a bracket T356 is secured tothe'bar`331 and the left hand end of `resistor 265 passes through thisbracket at A` 35| and is suitably fastened' thereto. A similar :bracketis provided at the opposite end of bar 331.

Referring now to the'potentiometer 254, the I slider35 is secured to the.block 339. as best inlldicatedin Figures 2 and 3, an insulated washerT352. being interposed between theslider and the block. As bestindicated in Figure 3the. opposite'4 .ends of resistor 305 are securedto bracket mem- :bers 354 and.355 which in .turn are secured to themainbracket Inember34.` It will be obvious that when the knob336 isrotated in a direction trans- -cverse -to the `plane of thepaper. so asvto -movev 4trocker 334, the sliderl306 .willmove with respectF-torresistor 365. If the knob is not moved in the lplaneof thepaper,the slider256 will not move f withrespect to resistor 265, the sliderLZGand re- Ifsistor 265'rocking as a unit about the axis of l.rockablemember 334. If,I onthe othervhand, the knob 33E! ismoved. in the planeof the vpaper with- `out 4any movement in adirection transverse toiithe-plane of the paper, the slider 266 will be :imoved `withA respectto resistor' 265 withoutlany VY'accompanying movement of slider-.366with re- 'zspectlto resistor 365. If the knob f33il is moved .iinneitheroi the planes discussed but is moved 'fsolas totilt thememberl256 in some other-direc- '."tion, both potentiometers252and 254will be ad- '..ijusted by relative amounts varying with the rela- -tivecomponents ofv movement of'member 256 yin A .fthe plane of the-paper andat right `anglesto `the plane ofthe paper, respectively.

.Zi'It is desirable that regardless of what direction st'herhandle 336istilted,- it returns automatically :to': center position as soon 'as itisreleased. We shave'taceordinglyprovided spring'means foracscomplishingthis. Referringfrst to .thetilting of^the'tv/o2bars351fandrf358. :"By adjusting the nut oi the bolt,theetensionffexerted.uponbars 351 and by springf359fcanfbe varied. Itwill be cbv'ousthatrthe tendencyofifbars`351 and 358 `byf'reason-iofthe'itension 'exertedzupon them by spring'f 3'59Lisztotend' to resistturning ofthe por- "the surrounding sleeve.- member" 32 1.

A similar biasing yarrangement is provided in 4connection'with'thelrockablemember 334. In

this case,v the twobars @are indicated by the seed together by a`spring'364 v surrounding a The free ends yof these ymembers bear againsta 'block at'the rght hand vend of the 'rockable-'member'corresponding toblock '33S at :the left hand end. It vvi11 -be apparentfrom the"previous" description-of the biasing -means comprising members'i351andf358 that the effect of the last describedbiasing means will be tomaintain therocker 3341in1the'position shown.

vThe potentiometer`i2-53 is actuated lupon rotation of themanuallymovable members '256. This potentiometer is `located within ahousing 364 Awhich iscarried by a bracket member 355 secured to theYlower portionof-sleeve ymember 321 so as "to be movable with sleevemember 321. "The sl'iderfZQI is secured to y'theend of a cylindricalmember`361 connected by` a splined connection "Thus, any'rotation'ofthe' tiltabley rod'256 will Hcausefmoven'ient of sliderf"=29l1relativeto the cir- `'cularresisto'r29ll. Afpin310'issecured'to the rod 1:2561and projects outward flthrou'ghf triangular opening 31| inthe1'sleeve'member'321. cThe effect of the biasing. spring 33l is..totend to cause pin 310 to normally occupy a position at the apex .of theftriangular opening. l `This tendsto maintainf-the-'slider -29`| inafcentral'position"with respect to t potentiometer-290 corresponding tothat .1 shown in'-Figure 1. i -The-pinandslot 31! tend to @perform a'further Yfunction which will be described in the .next fparagraph.

It is an'importantfeaturev of 4our'invention that the switch .bla-de 3 l5r is.-.moved into engagement with' switch blade. SIE-.feither \bymanually depressing :the rod 253;@by:rotation.` of knob `33D aboutitslongitudinalsaxis, or'fbyfmovement'oi the' knob.` 330" in 'suchl a'direction as to move slider' 266 of potentiometer 1252 away from itscentral-position. f As will'fbelapparent. from Fig- Vlures 2-.and 5,thefswitchlbladesland.3l6 are mounted` 1suitably:insu-lated from eachlother upon a bracket'318 secured to'vthe bracket member :365. a.Bearingfagainst a. camiollower portion of switch :bla-de 3 l 5 is a7collar :380v which is'journaled upon `Athe lrod' 256 soi as .to '-befreely: rotatable but longitudinally' fixed---with .-lrespect `to .therod.

This `collar-.38!) -carriesvpinsf I -whi'chextend` into a groove. inrod-'256 :to rotatably secure collar 380 thereto. r Pinsflcooperateiwitha--pair of cam xmembers'f333'fwhich. are secured. to Atherocker f rnember- 336.` asbest. indicated.l in yFigure 3. `The'cam1=membersf,383 are. providedwithrecesses 382 ing of rod 255 in theplane of the paper to move slider 256 with respect to resistor 255, thepins 35| must travel out oi the recesses 332 on to the circular portionof the cams 383. In doing so, the collar 385 is forced downwardly,pressing switch blade 3|5 into engagement with switch blade 3 I5. This,of course, causes closure of the switch constituted by the switchblades. If instead of knob 33|] being tilted in the plane of the paper,the knob is rotated, the collar 385i merely rotates with respect to rod255 and does not ride upon the lowermost portion of the cam surfaces ofcams 383. The effect of this rotation does, however, cause pin 311) tobe forced downwardly by reason of its cooperation with the walls of thetriangular opening 51|. This downward movement of shaft 255 in turncauses downward movement of collar 385 to effect movement of the switchblade 3l5 into engagement with switch blade SI5. Thus upon rotation ofknob 330 to actuate slider 29| with respect to resistor 290, the switchblades 3I5 and SIG are moved into contact making engagement. If at anyother time it is desired to close switch blades 3|5 and SI5, it will beobvious that downward pressure exerted on knob 53@ will push the rod 256downwardly, forcing collar 38|) against switch blade M5 to move it intocontact making engagement with switch blade 3|6. Thus, whenever slider255 is moved with respect to resistor 255 or slider 29| is moved withrespect to resistor 2%, the switch consisting of blades 3|5 and Slt isclosed. At other times, it may be closed by depressing knob 535.

The three potentiometers 251, 253, and 259 for adjusting the effectexerted by potentiometers 252, 253, and 255 are secured to the side ofthe housing 255 and as shown in connection with potentiometers 251 and259 are provided with shafts extending through the housing. Referring topotentiometer 251, a knob 315 is secured to the outer end of the shaftto permit adjustment of this potentiometer. A similar knob is providedin connection with each of the other potentiometers. If desired, a screwdriver adjustment may be substituted for the knob.

Operation of system In general, the ampliers I3, ifi, and I5 associatedwith the aileron. motor lli, the rudder motor Il, and elevator motor I2,respectively, are subject to input voltages which are determined by thenetworks associated with these ampliers. As has been indicated by thepreceding description of these networks, each of the networks comprisesa rebalancing potentiometer and various potentiometers responsive todierent conditions. Upon any one of these conditions being changed as aresult of a change in the attitude of a ship, one or more of thenetworks is unbalanced to cause movement of one or more of the motors.The movement continues until such time as the networks are rebalanced,partly by action of the rebalancing or follow up potentiometers. Thisaction will now be described in more detail.

With the various elements in the position shown in the drawing, nopotential is impressed upon the input circuits of ampliers i3, ifi, andI5. Referring first to the aileron amplifier I3, a series circuit can betraced from the upper terminal of this amplifier through conductor 165,slider 86, the lower portion of resistor S5, conductors 89 and 40|,slider 25, through the bridge 2|! to slider 29, conductor 402, slideri55, the upper portion of resistor 54, conductor E58, resistor |60,ground connections itl and 4M, and conductor 405 to the lower terminalof amplier I3. It is to be noted that this circuit included the lowerportion of resistor 85, the bridge 29, and the upper portion of resistorI. As previously explained, there is impressed across the lower portionof resistor B5 a potential which is dependent upon the position ofslider t5 and dependent in magnitude and phase upon the deflection ofsliders 64 and 56 from their mid-positions. Since these sliders are intheir mid-positions, no voltage is impressed across resistor andconsequently there is no voltage between the slider 85 and the lowerterminal of resistor 85. Similarly, the sliders 25 and 2B ofpotentiometers 2| and 22 are each in their mid-positions so that bridge263 iS balanced (assuming sliders 31 and 38 to be in their mid-position)and no voltage appears across the terminals of this bridge. The resistor|54 is connected in a series circuit as follows: from ground 218 throughconductor 214, the right hand portion of resistor 251, conductor 401,resistor |51, slider E58, conductor it, resistor |5rl, conductor E58,resistor E55, and ground connection IGI. It will thus be seen thatresistor |54 has impressed upon it a voltage equivalent to the combinedunbalance voltages of bridges |50 and 255. As previously explained, theexistence of an output voltage at either of these bridges is dependentupon the displacement of either slider it or slider 255 from itsmid-position. Since in both cases the sliders are shown in theirmid-positions, no voltage appears across these bridges and consequentlyno voltage is impressed across resistor i514. Consequently, the totalvoltage impressed upon amplifier lli has a value of zero.

Referring now to the rudder amplifier I4, a circuit may be traced fromthe upper terminal of this amplifier through conductor fits, slider |03,the lower portion of resistor m2, conductors |05 and MII, slider E25,through the bridge I2ii, slider l29, conductor dil, slider 253, theright hand portion of resistor 2%, conductors Sti and 303, slider |51,the upper portion of resistor |55, conductor |59, resistor I5t, groundconnections IGI and M3, and conductor dit to the lower terminal of theamplier. It will be Seen that these connections include the lowerportion of resistor |02, the bridge |20, the bridge 2M, and the upperportion of resistor 55. Since slider 98 is at its mid-position withrespect to the resistor 91, no voltage is impressed upon resistor E92and consequently none appears between the slider T03 and the lowerterminal thereof. Similarly, assuming that the centering potentiometersI33 and |34 are in their mid-positions, no potential exists acrossbridge |29. Since slider 299 is centered with respect to resistor 29B,no potential exists across bridge 25|. The resistor 55S is connected ina series circuit extending from ground connection 218 through conductor214, the right hand portion of resistor 251, conductor till, resistor|61, slider IBB, conductor ist, resistor 55, conductor |59, resistor it,and to ground at |5I. Thus, resistor E56 is connected in series withbridges |66 and 260 just as was resistor S52. As previously noted, novoltage appears across either of these bridges so that no voltageappears across resistor |55. Consequently, no voltage is impressed uponthe input of ampliiier It.

Considering now the elevator amplier, a series circuit may be tracedfrom the upper terminal of this amplier through conductor dit, slidery208, the lower portion of resistor 2M, conductors 2I0 and lill, slider225, the bridge 220, slider arr-near 229, conductor lll-8, slider' 3D3,the right hand portion of resistor'ill, conductor 3H), ground'connections 3| l and 42e, and conductor 42| to the lower terminal of theamplifier. Again, the voltage across the terminals of the ampliiierwould include any voltage between slider Ztl and the lower terminal ofresistor 2M, the unbalance voltage, if any', of bridge 220, and theunbalance voltage of bridge 2t?, if any. Since slider i195 isscenteredwith respect to resistor ist, no voltage appears across resistor 201.Similarly, bridges 22E' and 2.62 may be assumed to be balanced.

Under these balanced conditions, now let it be assumed that the planechanges its course slightly from that intended. This will cause thedirectional gyroscope 52 acting through the mechanical connection l tomove sliders lill', et, and |25 with respect to their associatedresistors. Let it beassumed that all of these ymovements' occur to. theright. The mover-nent of slider lili to the right Will cause a voltageto appear between slider es and the center tap, and this voltage, aspreviouslyv explained, will be impressed upon resistor B5; There willthus be impressed uponY resistor 85 a voltage which is a portion of thevoltage between slider iis and the center tap of resistor 63, dependingupon the position oi slider 6B; As previously explained, since sliders@5i and 6.6 are simultaneously moved, the voltage appearing acrossresistor is an exponential function ofthe movement ofA sliders 54andtill. While both ends of resistor 53 are connected together so thatthe voltage between slider 6d and the center tap of resistor 53 is notvaffected in phase bythe direction of displacement oi slider Eil, the fterminals of all potentiometers directly connected to a secondarywinding are positive with respect to their midpoints. It is, of course,understood that this condition Will immediately reverse during the nexthalf cycle but by considering the operations during a given half cycle,it :r

is--possible to readily deterr. ine the phase relationships between thevarious unbalance voltages. Assuming these conditions, the eiect of themovement of sliders 6e and ii just discussed isto render the-left handterminal of resistor E5 positive with respect to the right handterminal. Thel movement of slider et thus impresses across resistor 85 avoltage which causes the lower terminal of resistor S5 to be positivewith respect to the upper terminal. voltage of a certain phase to beimpressed upon motor l to cause movement of slider 2S to the right. anda corresponding movement ofthe ailerons to bank the plane in apredetermined direction necessary to effect a turn of the aircraft in amanner to restore the plane to its predetermined course. The movement ofslider 2-9tof they right tends to rebalance the network and'hence stopthe operation of the motor when the aileron position corresponds to thedeviation o f the gyroscope. This is the case because movement oftheslider 2li to the right tends to cause slider 25 tov become positivewith respect to slider 2.9. Asiv previously explained, the signal whichinitiated the turning of the ailerons was one This in turn causes awhich tended toraise the potential ofthe lower endvofr resista-nce 85with; respect to' slider 85. Hence'fithe voltage introduced into thecircuit between-thel amplier terminals by the movement of slider29opposes that introduced by reason ofv the deflection of sliders lil"vand 6B of the directional gyroscope potentiometers @il and Si.

Weretheaction which vhas been described so farfthe onlyl action whichoccurred', the aileron wouldibefdeected and-the plane would continue tobank 4more' andv more until theV direction was restored'. However, it isdesired to restore the ailerons-totheir streamlined position as soon asthe plane' isin. the proper degree'of bank. This is accomplishedI by theaction of the vertical gyroscope 21.. As soon as the plane enters abankgthe slider 25de Amoved by the Vertical gyroscope 21. This movementof slider 25 is `towards thel leftsoeasf to tend to cause slider 25 tobecome-positiverwith respect to slider 29. In other words the signalintroduced by movement of slider 257 opposes the signal introduced intothe directionalI gyroscopic potentiometers and 5l bymovement of sliderst4V and $5. Thusi a signal oil opposite phase is suppliedfto theamplifier i3A soas to= causemotor le to-rotate in the oppositedirection.f This in turn causes movement of slider 2.9 ofthe rebalancingpotentiometer back towards its.l center position corresponding to thestreamlinedposition of the ailerons. Allof these actions occur ratherquickly sovthat shortly vafter thedirectional gyroscopevhas deflectedsliders lill and: lili,` the ailerons will have been moved to bank theplaneand then willy have been moved back soi as toV bring slider 279back to the midposition.` The system will beV balanced by reason of thesignal from, the vertical gyroscope operated potentiometer 2| opposingthe signal introduced by the directionalI gyroscope throughpotentiometers and 6|. As the plane begins to appreachV the desiredcourse, the signal introduced by the directional gyroscope will decreasewith the result that the amplifier will supply the motor with a voltageof the proper phase to cause the aileronstobemoved in the oppositedirection to that previously considered. This. in turn will cause'thevertical gyroscope 2d to-move slider back` towards the mid-position. Thesuccessive decreases in the displacement -of sliders `Sil and66"frorritheir'mid-position and in the displacementofslider Z5 from itsmid-position will continue to occur almost continuously until theplaneisback. on itsicourse in straight and level ight, Thus.in theactionV described so far, the effect. ofV the directional gyroscope isto introduce a signal to cause the ailerons to be deflected insuch vamanner as to place the plane in a bank. The ailerons` are then movedback to their streamlined position, and as the plane returns to theproper "course, the ailerons are deected in 'the opposite direction tobring the plane back to a levelfposition. continuously.'

The deviation'of the aircraft from a predetermined direct'ion" of nightalso aifects the rudder byl operating the slider i255 of the directionalgyroscope potentiometer I2! of the rudder .ne-.+- work. Again;A theeffector the gyrosccpe to causel slider |25 to move to the right. Thiscauses an vunbalancedvoltage to appear between sliders |25 and |29 ofthebridge |20. Moreover, this voltageiisfsuch that during the conductivehalf cycle',` slider |-25"'s negative with respect to slider |2295'I-his'causes amplifier I4 to supply to motor |I aA signal of' such'Vphase as to cause the rudder All of these actions occur to ibefdeected*irrthe manner necessary to eftial of slider 98 and hence of slider itsto become positive with respect to the lower terminal of resistor lili.In other words, the eiect oi this is to introduce a voltage opposingthat introduced into the network by the operation of the directionalgyroscope on vpotentiometer lill. fect is to reduce the amount of rudderdisplacement and hence prevent skidding of the plane. As the planeapproaches the desired course, the amount ci bank is reduced aspreviously described so that the amount of si'gnal supplied by bridge@El is correspondingly reduced. Furthermore, the signal supplied by thedirectional gyrosccpe po tentiometer lili is reduced with the resultthat all of the potentiometers gradually approach their central positionshown in the drawing.

.t will be seen from the above that upon the deviation of the plane froma desired course, both the ailerons and the rudder are ope-rated toproduce a properly coordinated turn. The amount of aileron movement fora given deviation in the direction of the plane can be adjusted byadjustn ing the slider Eil of potentiometer til. As slider 8b is movedupwardly, the movement of the ailerons for a given deiiection ofthegyroscope is increased while movement of the slider in the op- 5 Now letit be assumed that the airplane rolls about its longitudinal axis so asto cause the vertical gyroscope 2l to move slider 2li with respect toresistor Let it again be assumed that the roll is in such a direction asto cause slider 2d to move to the right. This will cause slider tobecome negative with respect to slider 2S and supp-ly to the amplier asignal of a predetermined phase. This in turn will cause a current of avpredetermined phase to be supplied to the aileron motor lil, theresulting direction oi' operation of motor it being such as to cause theslider 2t to move to the right and to cause the ailerons to be deiiectedin a position tending to restore the plane to the desired attitude.

At the same time as the vertical gyroscope 2i moves slider 25, it alsomoves slider @3 to the right to introducey a signal into the rudderrietu work. Again, the effect of this signal is to cause slider Sit tobecome negative with respect to the center tap cr to cause slider tobecome negative with respect to the lower terminal of resistor ill?.This results in a signal of a prede-- termined phase being supplied tothe rudder motor l l to cause slider EZQ to move to the right withespect to resistor H28. The effect on the rudder of the operation of themotor in this direction is to cause the rudder to be so deflected as totend to turn the plane in a direction opposite to that which it wouldnormally tend to turn The ef" by reason of the bank. The reason for thisis that there has been no change in the direction of the plane, and ifsuch a change is to be prevented it necessary that the rudder oppose anytendency or the ship to change its direction by reason of the bank inwhich the ship has been accidentally placed. In other words, theailerons seek to restore the ship to the proper attitude While therudder keeps the ship from changing its course by reason of the bank inwhich it is placed.

A further action takes place at the same time. The vertical gyroscope 2lalso acts to position slider ldd of the potentiometer lul. Regardless ofwhich direction the slider i913 is moved, the voltage impressed uponresistor Ziil is of the same polarity. As previously explained, thepresence oi this voltage causes amplier l5 to supply a current of apredetermined phase to the motor l2. The phase of this current is suchas to cause the motor to tilt the elevators upwardly sfo as to tend toraise the airplane. The need for this is that whenever a plane is placedin a bank either intentionally or by reason of some external force, theplane tends to lose altitude. By supplying a 1 signal causing theelevators to be raised, this tendency of the ship to lose altitude isprevented. it is to be noted here that in the turn previously referredto in connection with the deviation of the airplane from the desiredcourse, the same action took place as soon as the plane was placed intoa bank. In other words, the elevators were derlected upwardly so as tominimize any tendency of the plane to lose altitude.

in each of the three networks, the movement of the control surface islimited by the action of the rebalancing potentiometer which in eachcase moves in a direction to rebalance the network. As the planegradually approaches the straight and level condition it originallyassumed, the deflection or the vertical gyroscope decreases so that thesignal supplied to the several networks decreases with a resultingdecrease in the deflection of the control surfaces. Gradually, each ofthe control surfaces returns to its streamlined position as the planeapproaches its desired attitude.

l'low let it be assumed that the aircraft alters its pitch from thedesired one. This will cause the vertical gyroscope El to move slider225. Let

` it be assumed that the plane has started to climb.

This will cause slider 225 to move to the right. Under these conditions,slider 225 will become negative with respect to slider 229 so as t0:cause a signal to be supplied to amplifier l5, of such phase relationas to cause the motor l2 to be driven in a direction to move slider 229to the right. This direction of rotation is such as to cause movement ofthe elevator downwardly so to cause the ship to tilt back towards th-edesired course. As the plane is tilted back, the displacement of slider25 will decrease with the result that the bridge will be unbalanced inthe opposite direction to cause motor l2 to drive the elevators backtowards their streamlined position. This action will continue until theairplane is again assuming the proper pitch.

in the action which has been described so far, no provision has beenmade `for changing the course or `pitch of the aircraft when it isdesired to turn or climb. The bridge l5@ provides one means foraccomplishing a turn. It will be noted that the circuit traced toamplifier i3 included 'the upper portion of resistor lei ofpotentiometer l Similarly, the circuit to lamplier I4 included the upperportion of resistor l 516 yof poten- 17 Itiometer |53. It will also berecalled that the voltage across resistors |54 and |56 was `determinedby the voltage across the terminals of bridges |50 and 260. Thus, anychange made in bridge |59, for example, affects both the rudder andaileron control networks.

This action will now be described in slightly more detail. Let it beassumed that the pilot desires to turn his aircraft in a predetermineddirection requiring movement of slider |68 to the right. This isaccomplished by actuation of knob 13 which causes cam |15 to be rotatedin a counter-clockwise direction. The movement of slider |63 to theright .applies a voltage of a predetermined phase to both resistors |54and |56. Variable portions of this voltage are thus introduced into boththe aileron and rudder networks. The relative portions of this voltageintroduced into the two networks is dependent upon the relative settingsof sliders |55 and |51 of the trim- .v

ming potentiometers |52 and |53. It will be apparent that both therudder and aileron networks are unbalanced so as to cause movement ofboth of these surfaces. This movement furthermore is in such a directionas to place the plane in a banked turn in the desired direction. If somemeans were not provided to render the directional gyroscope temporarilyinoperative in positioning the various sliders controlled by it, thedirectional gyroscope would immediately attempt to restore the plane tothe course which it is set to maintain, and as soon as the turn controlwere restored to its original position, the directional gyroscope wouldimmediately proceed to restore the plane to its original heading. This,of course, is not desirable where a turn is to be made. Consequently,means are provided `for locking :the mechanical connections between thedirectional gyroscope and :the mechanical connections 61 leading to thevarious sliders positioned by the directional gyroscope. As soon asswitch blades llt and |11 are moved together by reason of movement oflthe cam |15, an energizing circuit is established to the lock l69 -asfollows: from the positive terminal of a battery 425 through conductors426 and 421, switch blades |11 and |16, conductors 428 and 429, lock 59,and conductor 432 to the negative terminal of battery 425. soon as lock|69 is thus energized, the sliders '64, 56, and are locked in position,and while the gyroscope turns with respect to the plane, the mechanicalconnections v|31 merely slip with respect to the gyroscope.

Although the directional gyroscope is locked,

the vertical gyroscope is still free to move slider i 25 ofpotentiometer 2| in the aileron network and slider 98 of potentiometer96 in the rudder network. In each case, the movement of the slider byythe vertical gyroscope is in a direction tending to restore theairplane surface to the streamlined -position it had before the turncontrol knob was actuated. This is desirable in that as soon as theplane is placed into a bank, the ailerons should be streamlined so as tomaintain the plane in exactly the desired bank. Similarly, the ruddermovement should be reduced so as to avoid overshooting of the plane.

As the plane approaches the desired course, the turn control is turnedback to the normal position and the various surfaces are deflected inthe opposite direction. In the case of the ailerons, this has the effectyof ftilting the plane back to a level position so as to cause the planeto continue in horizontal andlevel flight. The simultaneous reversal ofthe rudder results in a coordinated .ASI

recovery from'the turn which would not be possible merely by movement ofthe ailerons in the opposite direction. The pilot should preferably holdthe turn control slightly deflected from ycenter so as to maintainswitches |16 'and 11 closed until the ship has resumed straight andlevel flight. Otherwise, the lock in connection with the direction-a1gyroscope will :be released while the ship is stillin a turn and willimmediately attempt .to correct the condition with the result that theattitude 0f the plane maintained by the gyroscopes will be altered withrespect to that which is desired.

The operation of our improved manual controller, as far as the VsystemVis concerned, will now be discussed. Let it be assumed that the pilotdesires to turn in a predetermined direction. The knob 33|) is graspedand'moved in the plane of the paper in the direction corresponding tothe desired turn. Let it be assumed that this direction is to the leftso as to cause a movement of slider 266 to the vright on resistor 265 asviewed in the drawing. This `will `cause a potential to appear betweenslider 266 and the center tap of resistor 265. It lwill be recalled thatboth resistors |54 and |56 are connected in series with both bridges and260. Hence, the movement of slider 266 with'respect to the center tap ofresistor 265 will apply a voltage across resistors |54 and |56. Thisvoltage will be introduced into both .the rudder and aileron networks inmuch the same manner as when the turn control was operated. The positionof slider 258 will determine the magnitude of the signal that isintroduced into the rudder and aileron networks for a given movement ofthe knob 33|). The relative amount of rudder and aileron movement willbe determined by the setting of sliders |55 and |51. The effect upon theoperation of the rudder and ailerons will be exactly the same as inconnection with operation of the turn control of bridge. |50. In thecase of our manual controller, it is also necessary to provide somemeans for energizing the lock associated with the directional gyroscope,if a change in direction is to be eiected. As was noted in thedescription of the details of our controller, a movement of the knob 330in the plane of the paper caused collar 38B to move downwardly to causeengagement of the switch blade 3|5 with switch blade 3|6. This resultsin a circuit being established to the lock 69 asfollows: from the lowerterminal of battery 425 through conductors 426 and 433, switch blades3|5 and 3|6, conductors 4'34 and 429, lock 69, and

conductor 430 to the other terminal of the battery 425. Thus, again,during the turn, the lock of the directional gyroscope is automaticallyrendered effective upon a turn being instituted. In the case of thedirectional gyroscope, it was necessary to maintain the knob slightlyoff center after the turn was completed in order to keep the switchblades` |16 and |11 in contact making engagement until the ship returnedto its straight and level position. In the present device we haveprovided a means to maintain this switch closed after the knob 336 hasreturned to its normal upright position. All that is necessary to do isto maintain the knob 330 depressed after the knob is returned -to itsoriginal position by the action of the spring pressed blades 351 and35i). As long as the knob 330is depressed, switch blades 3|5 and 3|6 aremaintained closed. Hence, even though the knob is in its centralposition, the directional armlock may be maintained energized until theplane is in its desired attitude. We have 19 thus provided a means forconveniently enabling the pilot to delay placing the directionalgyroscope back in control of the airplane until the ship is headed inthe proper direction.

II" it is desired to climb or dive, the knob 33t is grasped and movedthrough a plane at right angles to the plane of the paper. The movementshould be in a direction corresponding to the desired change in pitch ofthe plane. Let it be assumed that it is desired to cause the plane toclimb. In that event, the knob 33o is pushed into the plane oi the paperso as to cause slider Seli to be moved to the left with respect toresistor Stl (as viewed in Figure l). The effect of this is to causeslider 305 to become positive with respect to the center tap of resistorttt and to introduce into the circuit a signal of such phase as to causethe motor l2 to drive the elevator upwardly. The elevator tends toassume a position corresponding to the amount of deflection of sliderlfi. As soon as the .plane starts to climb, however, the verticalgyroscope 2l detects the climb and moves slider 225 to the left tooppose the effect of the movement of slider 366 to the right. As aresult, an unbalance voltage of the opposite polarity is supplied by theamplifier to the motor l2 to return the elevator towards its streamlinedposition. This action continues until the elevator is back in itsstreamlined position. This is desirable since the desired degree ofclimb has been initiated and will continue until the elevator isdeflected in the opposite direction. As soon as the desired climb hasbeen completed, the knob 330 is released to permit the knob and rodassembly to return to a neutral position under the action of springpressed blades 362 and `When this happens, the only signal present inthe network is' that introduced by the displacement of the slider 225 ofthe potentiometer positioned by the vertical gyroscope, and the eiiectof this signal is to cause the elevator to run in a direction oppositeto that in which it was previously deilected. In other words, thetendency of the gyroscope is to cause the airplaneto assume the pitch itpossessed before the climb had been made.

In some cases, it is desirable to turn the aircraft by means of therudder alone. This is called skidding One instance inwhich this isdesirable is when a group of airplanes are flying in close formation. Insuch a case, it is undesirable to bank the airplane too much becausewhen the airplane'comes out of the bank it may be discovered that theplanes are so close together as to cause collision. We have accordinglyprovided means for operating the rudder without affecting the ailerons.rIhis is accomplished by rotation of knob 330 and hence of shaft 256 tomove the slider 291 with respect to the resistor 259 of potentiometer253, V/'hen this is done, a voltage appears between the slider 2&1 andthe center tap of resistor 2.9i). This voltage appears between slider|29 of the rebalancing potentiometer and the slider E57 of the trimmingpotentiometer, and hence is eiective regardless of whether any signal isintroduced in either bridges lli@ or itil to introduce a voltage in therudder network. The phase of this voltage will be dependent upon thedirection of displacement of slider 29| from the mid-position ofresistor 290 which in turn is dependent upon the direction of rotationof knob ddd. The result of such a rotation of knob 33t will be to causethe rudder to turnby an amount proportional to the rotation of the knob.Rotation of knob 336, as previously explained, causes downward movementof shaft 256 to effect closure of switch blades 315 and BIG. When thishappens the lock te is energized through the circuit traced previouslywith the result that the directional gyroscope has no effect upon any ofthe potentiometers normally controlled by it. As soon as the knob 33B isthen returned to its original position and released, the directionalgyroscope again starts to control the ship to maintain the new directionof flight. As with the turn effected by the rudder and ailerons, it isdesirable to maintain the switch blades 3HE and Siti closed for a briefperiod of time after the potentiometer has been moved back to itscentral position in order to permit the plane to return to the coursefor which it is set before placing it under the control of thegyroscope. This is done, as with normal turns, by depressing knob 339for a short period of time after is returned to its neutral position.

While the action described above has been in connection with only onedirection of movement of the various controls, it is to be understoodthat in every case, where the condition changes in the oppositedirection or where the manual operator is moved in the oppositedirection to 'that considered, the effect on all o-f the control isopposite to that discussed. The only exception is in the effect onelevator of the plane being placed into a bank. In this instance, theelevator is moved so as to tend to cause the plane to rise regardless ofthe direction in which the ship is banked.

It will be seen that we have provided an extremely simple and readilymanipulable manual control for altering the course of an aircraftcontrolled by an automatic flight control system.

With our control, by means of the operation of a single knob, the planecan be made to either turn or alter its pitch to any desired degree. By

moving the control knob 33t at an angle to both planes of normalmovement, the plane can be made to either turn or alter its pitch to anydesired degree. By moving the control knob 33t at an angle to bothplanes of normal movement, the plane can be made to bank and alter itspitch simultaneously. Furthermore, by manipulation of the same knob, itis possible to maintain the lock on the directional gyroscope engagedafter the knob has returned to its neutral position. In addition, ourcontrol provides means for turning by means of the rudder alone. It willfurthermore be seen that we have provided a new and highly eilectivearrangement for operating a plurality of circuit controlling devices bya single manually manipulable member.

While we have shown a specic embodiment of our device for purposes ofillustration, it is to be understood that the invention is limited onlyby the scope of the appended claims.

We claim as our invention:

1. In control apparatus for an aircraft having a rst motor forpositioning a iirst airfoil surface for controlling the direction offlight and a second motor for positioning an airfoil surface forcontrolling the pitch of the aircraft; first motor controlling meansincluding a devi-ce adapted to respond to the deviation of an aircraftfrom a predetermined direction of iiight and adapted to automaticallycontrol said rst motor, second motor controlling means including adevice adapted to respond to the deviation of the pitch of an aircraftfrom a predetermined attitude and adapt-- ed to automatically controlsaid second motor, device adapted to respond to the deviations of theaircraft about the roll axis and adapted to control said second motor, atiltable member,

through one plane to modify the action of said first motor controllingmeans so that the latter is effective to cause the aircraft to turn, andmeans operated when said member is tilted through another plane tomodify the action of said second motor controlling means so that thelatter is effective to cause the aircraft to alter its itch.

2. In control apparatus for an aircraft having a first motor forpositioning an airfoil surface for controlling the direction of fiightand a second motor for positioning an airfoil surface for controllingthe pitch of the aircraft; first motor controlling means including adevice adapted to respond to the deviation of said aircraft from apredetermined direction of night for automatically controlling saidfirst motor, second motor controlling means including a device adaptedto respond to the deviation of the pitch of said aircraft from apredetermined attitude and a device adapted to respond to deviations ofthe craft about the roll axis for automatically controlling said secondmotor, manually a-ctuable means, means operated when said manuallyactuable means is moved in one manner to modify the action of said firstmotor controlling means so that the latter is effective to cause theaircraft to turn, means operated when said manually actuable means ismoved in a different manner to modify the action of said second motorcontrolling means so that the latter is effective to cause the aircraftto alter its pitch; and spring means to lcause said manually actuablemeans when released to return to the position assumed before initiationof the manual operation.

3. In control apparatus for an aircraft having first and second motorsrespectively positioning airfoil surfaces for controlling the directionof flight and the pitch of the aircraft; first motor controlling meansincluding a device adapted to respond to the deviation of an aircraftfrom a predetermined direction of flightl for automatically controllingsaid first motor, second motor controlling means including a deviceadapted to respond to the deviation of the pitch of an aircraft from apredetermined attitude and a device responsive to deviations of theaircraft about the roll axis for automatically controlling said secondmotor, a tiltable member, means operated when said member is tiltedthrough one plane to modify the action of said rst motor controllingmeans to adapt the latter to cause the aircraft to turn, means operatedwhen said member is tilted through another plane to modify the action ofsaid second motor controlling means to adapt the latter to cause theaircraft to alter its pitch, and spring means to cause said member toreturn to a neutral position when released.

4. In control apparatus for an aircraft having a plurality of airfoilsurfaces, a first motor for so positioning a iirst of said airfoilsurfaces as to affect the direction of flight, a second motor for sopositioning a second of said airfoil surfaces as to affect the tilt ofthe aircraft about its longitudinal axis, and a third motor for sopositioning a third of said airfoil surfaces as to affect the pitch ofthe aircraft, first motor controlling means including a device adaptedto respond to the deviation of said aircraft from a predetermineddirection of flight for automatically controlling said first motor,second motor controlling means including both a device adapted torespond to the tilting of said aircraft about its longitudinal axis anda device adapted to respond to the deviation of said aircraft from apredetermined direction of flight for controlling said second motor,third motor controlling means including a device adapted to respond tothe deviation of the pitch of said aircraft from a predeterminedattitude for automatically controlling said third motor, a memberadapted to be tilted through two planes, means operated when said memberis tilted Vthrough one plane to modify the action of both said first andsecond motor controlling means to adapt them to place the aircraft in aproperly banked turn, and means operated when said member is tiltedthrough another plane to modify the action of said third motorcontrolling means to adapt the latter to cause the aircraft to alter itspitch.

5. In control apparatus for an aircraft having first and second motorsrespectively positioning airfoil surfaces for controlling the directionof flight and for controlling the tilt of the aircraft about itslongitudinal axis; first motor controlling means including a deviceadapted to respond to the deviation of said aircraft from apredetermined direction of flight for automatically controlling said rstmotor, second motor controlling means including both a device adapted torespond to the tilting of an aircraft about its longitudinal axis and adevice adapted to respond to the deviation of an aircraft from apredetermined direction of flight for controlling said second motor, amanually movable member, means operated when said member is moved 'inone manner to modify the action of only said first motor controllingmeans to adapt the latter to turn said aircraft without appreciablybanking the same, and means operated when said member is moved in adifferent manner to modify the action of both said first and secondmotor controlling means to adapt them to place the aircraft in aproperly banked turn.

6. In control apparatus for an aircraft having a plurality of airfoilsurfaces, a first motor for so positioning a rst of said airfoilsurfaces as to affect the direction of flight, a second motor for sopositioning a second of said airfoil surfaces as to affect the tilt ofthe aircraft about its longitudinal axis, and a third motor for sopositioning a third of said airfoil surfaces as to affect the pitch ofthe aircraft, rst motor controlling means including a device adapted torespond to the deviation of said aircraft from a predetermined directionof ight for automatically controlling said first motor, second motorcontrolling means including both a device adapted to respond to thetilting of an aircraft about its longitudinal axis and a device adaptedto respond to the deviation of an aircraft from a predetermineddirection of flight for controlling said third motor, third motorcontrolling means including a device adapted to respond to the deviationof the pitch of an aircraft from a predetermined attitude forautomatically controlling said second motor, a manually movable member,means operated when said member is moved in one manner to modify theaction of only said first motor controlling means to adapt it to causethe aircraft to turn Without appreciably banking the same, meansoperated when said member is moved in a different manner to modify theaction-of both said first and second motor controlling means to adaptthem to place the aircraft in a properly banked turn, means operatedwhen said member is moved in a third manner to modify the action of saidthird motor controlling means to adapt it to cause the aircraft to alterits pitch.

'7. In control apparatus for an aircraft having a plurality of airfoilsurfaces, a first motor for so positioning a first of said airfoilsurfaces as to affect the direction of flight, a second motor for sopositioning a second of said airfoil surfaces as to affect the tilt ofthe aircraft about its longitudinal axis, and a third motor for sopositioning a third of said airfoil surfaces as to affect the pitch ofthe aircraft; rst motor controlling means including a circuitcontrolling device adapted to respond to the deviation of said aircraftfrom a predetermined direction of night for automatically controllingsaid first motor, second motor controlling means including both acircuit controlling device adapted to respond to the tilting of anaircraft about its longitudinal axis and a circuit controlling deviceadapted to respond to the deviation of an aircraft from a predetermineddirection of flight for controlling said second motor, third motorcontrolling means including a circuit controlling device adapted torespond to the deviation of the pitch of an aircraft from apredetermined attitude for automatically controlling said third motor, amanually tiltable member, means including a circuit controlling deviceconnected to both said first and second motor controlling means andoperated when said member is tilted through one plane to modify theaction of both said first and second motor controlling means to adaptthem to place the aircraft in a properly banked turn, and meansincluding a circuit controlling device connected to said third motorcontrolling means and operated when said member is tilted throughanother plane to modify the action of said third motor controlling meansto adapt it to cause the aircraft to alter its pitch.

8. In combination, an aircraft having an airfoil surface for controllingthe direction of night, a motor for positioning said airfoil surface,motor controllingv means including a device adapted to respond to thedirection of flight of said aircraft for controlling said motor, amanually movable member, means operated when said manually movablemember is moved in a predetermined manner to modify the action of saidmotor controlling means to cause said aircraft to turn, means renderedeective by movement of said member to render temporarily inoperativesaid device responsive to the direction of flight as long as said memberis moved in said predetermined manner away from a normal position, andfurther means for temporarily maintaining said means rendered effectiveby movement of said member effective after return of said member to itsnormal position.

9. In control apparatus foi an aircraft having a motor for positioningan airfoil surface for controlling the direction of flight; motorcontrolling means including a device adapted to respond to the directionof flight of such an aircraft and adapted to control said motor, amanually tiltable mem-ber, means operated when said manually movablemember is tilted in one plane to modify the action of said motorcontrolling means so that the latter is effective to cause the aircraftto turn, means rendered effective by movement of said member to rendertemporarily inoperative said device which is adapted to respond to thedirection of flight as long as said member is tilted in said one planeaway from a normal position, spring means for returning said tiltablemember to said normal position, and further means for temporarilymaintaining said means effective by movement of said member effectiveafter return of said member to said normal position.

10. In control apparatus for an aircraft having a motor for positioningan airfoil surface for controlling the direction of flight; motorcontrolling means including a gyroscope and a device normally positionedby said gyroscope through a connection capable of slipping so as tomaintain a predetermined direction of flight, a manually movable member,means operated when said manually movable member is moved in apredetermined manner to modify the action of said motor controllingmeans to adapt the latter to cause the aircraft to turn, means renderedeffective by movement of said member to lock said device With respect tosaid craft so as to cause slippage between said gyroscope and saiddevice, as long as said member is moved in said predetermined manneraway from a normal position, and further means for temporarilymaintaining said locking means effective after return of said member toits normal position.

ll. In control apparatus for an aircraft having first and second motorsrespectively positioning airfoil surfaces for controlling the directionof flight and the tilt of the aircraft about its longitudinal aXis;first motor controlling means including a device adapted to respond tothe deviation of an aircraft from a predetermined direction of flightfor automatically controlling said first motor, second motor controllingmeans including both a device adapted to respond to the tilting of anaircraft about its longitudinal axis and a device adapted to respond tothe deviation of the aircraft from a predetermined direction of flightfor controlling said second motor, a manually movable member, meansoperated when said member is moved in one manner to modify the action ofonly said first motor controlling means to adapt the latter to cause anaircraft to turn Without appreciably banking the same, means operatedwhen said member is moved in a different manner to modify the action ofboth said rst and second motor controlling means to adapt them to placethe aircraft in a properly banked turn, and means effectiveautomatically when said member is moved in said second manner to renderineffective said device winch is adapted to respond to the deviation ofthe aircraft from a predetermined direction of flight.

12. In control apparatus for an aircraft having rst and second motorsrespectively positioning airfoil surfaces for controlling the directionof flight and the tilt of the aircraft about its longitudinal aXis;first motor controlling means including a device adapted to respond tothe deviation of an aircraft from a predetermined direction of flightfor automatically controlling said first motor, second motor controllingmeans including both a device adapted to respond to the tilting of anaircraft about its longitudinal axis and a device adapted to respond tothe deviation of an aircraft from a predetermined direction of flightfor controlling said second motor, a manually movable member, meansoperated when said member is moved in one manner to modify the action ofonly said rst motor controlling means to adapt the latter to cause theaircraft to turn without appreciably banking the same, means operatedwhen said member is moved in a second manner to modify the action ofboth said rst and second motor controlling means to adapt them to placethe aircraft in a properly fbanked turn, and means effectiveautomatically when said member is moved in either said one or saidsecond manner to render ineffective said ldevice which is adapted torespond to the deviation 'of the aircraft from a predetermined directionof night.

13. In control apparatus for an aircraft having rst and second motorsrespectively positioning airfoil surfaces for controlling the directionof flight and pitch of the aircraft; first motor controlling meansincluding a device adapted to respond to the deviation of an aircraftfrom a predetermined direction of flight for automatically controllingsaid first motor, second motor controlling means including a deviceadapted to respond to the deviation of the pitch of an aircraft from apredetermined attitude for automatically controlling said second motor,a manually tiltable member, means operated when said member is tilted inone direction to modify the action of said first motor controlling meansto adapt the latter to cause the aircraft to turn, means operated whensaid member is tilted 'in a different direction to modify the action ofsaid second motor controlling means to adapt the latter to cause theaircraft to alter its pitch, and means effective automatically when saidmember is moved in said first direction to render ineiective said devicewhich is adapted to respond to the deviation of the aircraft from apredetermined direction of flight.

14. In control apparatus for an aircraft having rst and second motorsrespectively positioning airfoil surfaces for controlling the directionof flight and the pitch of the aircraft; first motor controlling meansincluding a device adapted to respond to the deviation of an aircraftfrom a predetermined direction of flight for automatically controllingsaid first motor, second motor controlling means including a deviceadapted to respond to the deviation of the pitch of an aircraft from apredetermined attitude for automatically controlling said second motor,a manually movable member, means operated when said member is moved inone manner to modify the action of only said first motor controllingfmeans to adapt the latter to cause the aircraft to turn, means operatedwhen said member is moved in a different manner to modify the action ofsaid second motor controlling means to adapt the latter to cause theaircraft to alter its pitch, spring means effective always to returnsaid member to a normal position when released, and means effectiveautomatically when said member is moved in said rst manner and as longas said member is away from said normal position to render ineffectivesaid device which is adapted to respond to the deviation of the aircraftfrom a predetermined direction of flight.

l5. In control apparatus for an aircraft having rst and second motorsrespectively positioning airfoil surfaces for controlling the directionof flight and the pitch of the aircraft; lirst motor controlling meansincluding a device adapted to respond to the deviation of an aircraftfrom a predetermined direction of flight for automatically controllingsaid rst motor, second motor controlling means including a deviceadapted to respond to the deviation of the pitch of an aircraft from apredetermined attitude for automatically controlling said second motor,a manually movable member, means operated when said member is moved inone manner to modify the action of said first motor controlling means toadapt the latter to cause the aircraft to turn, means operated when saidmember is moved in a different manner to modify the action of saidsecond motor controlling means to adapt the latter to cause the aircraftto alter its pitch,

spring means eiective' always to return said member to a normal positionwhen released, means effective automatically when said member is movedin said first manner and as long as said member is away from said normalposition to render ineffective said device which is adapted to respondto the deviation of the aircraft from a predetermined direction offlight, and means for temporarily maintaining said last named meanseffective after return of said member to said normal position.

16. In a device for selectively controlling a plurality of motorcontrolling circuits each comprising variable impedance means; aplurality of impedance units, an adjusting means for each of saidplurality of units, a member rockable about its longitudinal axis, atiltable member pivotally secured t'o said rockable member about an axisperpendicular to the longitudinal axis of said rockable member so thatwhen said tiltable member is tilted about said last-named pivotal axis,it tilts with respect to said rockable member and when said tiltablemember is tilted about the axis of said rockable member, said tiltablemeinber and rockable member are moved together, operative connectionbetween the 'adjusting means of one of said impedance units and tiltablemember for movement of said adjusting means when said member is tiltedabout its pivotal axis, a further `operative connection between theadjusting means of another of said impedance units and saidl rockablemember, said tiltable member being not only pivotally secured to saidrockable member but also rotatable about its own longitudinal axis, anda connection between the adjusting means of another of said impedanceunits and said tiltable member for movement of said adjusting means uponrotation of said tiltable member about its longitudinal axis.

17. In a device for selectively controlling a plurality of electriccircuits; a plurality of circuit controlling devices, a member rockableabout its longitudinal axis, a tiltable member pivotally secured to saidrockable member about an axis perpendicular to the longitudinal axis ofsaid rockable member so that whenv said tiltable member is tilted aboutsaid last-named pivotal axis, it tilts with respect to said rockablemember and when said tiltable member is tilted about the axis of saidrockable member, said tiltable member and rockable member are movedtogether, an operative connection between one of said circuitcontrolling devices and said tiltable member for operation of saidcircuit controlling device when said member is-tilted about its pivotalaxis, a further operative connection between another of said circuitcontrolling devices and said rockable member for operation of thatcircuit controlling device When said rockable member is rocked, saidtiltable member being longitudinally movable along its longitudinal axisWith respect to said rockable member, and an operative connectionbetween a third of said circuit controlling devices and said tiltablemember for operation of said third circuit controlling device when saidmember is longitudinally moved.

18. In a device for selectively controlling a plurality of electriccircuits; a plurality of circuit controlling devices, a member rockableabout its longitudinal axis, a tiltable member pivotally secured to saidrockable member about an axis perpendicular to the longitudinal axis ofsaid rockable member so that when said tiltable member is tilted aboutsaid last-named pivotal axis, it tilts With respect to said rockablemember and 27 when said tiltable member is tilted about the axis of saidrockable member, said tiltable member and rockable member are movedtogether, an operative connection between one of said circuitcontrolling devices and said tiltable member for operation of saidcircuit controlling device when said member is tilted about its pivotalaxis, a further operative connection between another of said circuitcontrolling devices and said rockable member for operation of thatycircuit controlling device when said rockable member is rocked, saidtiltable member being not only pivotally secured to said rockable memberbut also rotatable about and longitudinally movable along its ownlongitudinal axis, and connections between said tiltable member andthird 'and fourth of said circuit controlling devices for operating said:third circuit vcontrolling device when said tiltable member islongitudinally moved and said fourth circuit controlling device whensaid tiltable member f.

is rotatable about its longitudinal axis.

19. In a ldevice for selectively controlling a plurality of circuitseach including contacts and a wiper coacting with said contacts, andadjustable means for each Wiper, a member rockable about an axis, asecond member pivoted to said rockable member about an axisperpendicular to the said axis so that when said pivoted member pivotsabout its axis it rotates with respect to said rockable member and whensaid pivoted member is moved about the axis of the rockable member therockable member and the pivoted member move together, an operativeconnection from the pivoted member to one wiper for adjustment when saidpivoted member is rotated about its pivot on said rockable member, anoperative connection from said rockable member to another wiper, saidpivoted member being not only pivoted to said rockable member but alsorotatable about its own longitudinal axis, and an operative connectionfrom said pivoted member to a third Wiper for movement of said wiperupon rotation of said pivoted member about its longitudinal axis.

20. In control apparatus for an aircraft having a first motor forpositioning an airfol surface for controlling the direction of flightand a second motor for positioning an airfol surface for controlling thepitch of the aircraft; motor controlling means including a deviceadapted to respond to the deviation of an aircraft from a predetermineddirection of flight for automatically controlling said rst motor, secondmotor controlling means including a device adapted to respond to thedeviation of an aircraft from a predetermined attitude for automaticallycontrolling said second motor, means including a device adapted torespond to the deviation of the aircraft about the roll axis forcontrolling said second motor, a manually tiltable member, meansoperated when said member is tilted in one direction to modify theaction of said i'lrst motor controlling means So that the latter iseffective to cause the aircraft to turn, and means operated when saidmember is tilted in a different direction to modify the action of saidsecond motor controlling means so that the latter is effective to causethe aircraft to alter its pitch.

21. Control apparatus for an aircraft having a rst airfol surface forcontrolling the direction of flight, a second airfol surface forcontrolling the tilt of the aircraft about its longitudinal axis, yand athird airfol surface for controlling the pitch of the aircraft, saidapparatus comprising: a manually operable member movable about threerespectively perpendicular axes; means operated by said member onmovement thereof about a rst of said axes to cause only said rst airfolsurface to move to turn the aircraft Without appreciably banking thesame; means operated by said member on movement thereof about a secondof said axes to cause both said first and second airfol surfaces to moveto place said aircraft in a banked turn; and means operated by saidmember on movement thereof about a third of said axes to cause saidthird airfol surface to move to cause the aircraft to alter its pitch.

ROBERT J. KUTZLER.

THEODORE J. WILSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 539,863 Faure et al. May 28, 18951,239,837 Sperry Sept. 11, 11917 1,418,335 Sperry June 6, 1922 1,553,262Perna Sept. 8, 1925 2,005,061 Thomas June 18, 1935 2,144,616 CarlsonJan. 24, 1939 2,162,862 Protzen June 20, 1939 2,190,390 Thiry Feb. 13,1940 2,198,523 Adams Apr. 23, 1940 2,270,875 Hanson et al. Jan. 27, 19422,277,883 Rich Mar. 31, 1942 2,280,116 Carlson Apr. 21, 1942 2,379,778Allen July 3, 1945 2,397,978 Paulus et al Apr. 9, 1946 2,398,421 Frischeet al Apr. 16, 1946

